技术支持
■ What is crystal of quartz device?
What is 'crystal' of crystal device? Crystal is a monocrystal made of Si and O2. Amethyst, citrine and rose quartz used for accessories are also crystals. These crystals are discolored by metal oxide. Crystal is filled with mysterious beauty and owns a property of piezoelectric effect — the generation of electric polarization when given mechanical stimulus which causes deformation. On the other hand, if given electrical polarization, it is mechanically deformed in terms of property, which is called inverse piezoelectric effect. The crystal device is an electric part manufactured by crystal.
The crystal device made by DAISHIKU CORP. (KDS) is used in familiar electronic equipment in our daily life such as AV equipment (including DVD and digital television), automotive electronics and game machines. Electric equipment is controlled by information transmission carried out by computer and KDS’ crystal devices play a very important role in transmitting this information. In another words, a crystal device, such as a crystal resonator will keep oscillating the specified signal and plays the same role as a heart sending blood into body. That is why it is considered one of the most important electronic mechanism.
■ How is it turned into electric device?
How is it turned into electric device? In the following section, this question will be answered in reference to crystal resonators.
(1) How to develop synthetic quartz crystal
Gigantic pressure vessel called autoclave is filled with alkaline solution and its upper half is seed quartz (plate of pure crystal with less flaw in crystal arrangement) and its lower half is raw material of natural crystals called lasca. Then re-crystalization is generated under high temperature and high pressure conditions with 300- 400 deg.C and 1000- 1500 atmospheric pressure. This is how synthetic quartz crystal is made. The development stage differs from crystal to crystal, usually taking a couple of months. Since the quality of synthetic quartz crystal is the biggest determinant in deciding a good or bad crystal resonator, KDS employs the most stringent control system so that the synthetic quartz crystal with highest level quality can be produced. It is free from impurities so that it can be used for electronics parts. At this stage, synthetic quartz crystal is still heavy and big, so it may be hard to imagine how it is processed into a crystal resonator, which is smaller than a grain of rice.
(2) Processing into a crystal blank
Crystal is colorless and clear substance and seems to have no directional property whichever part is used because its axis is invisible. However, crystal does have directional property and it is therefore necessary to identify the crystal axis to make it functional as an electronics component. This process is called the lumbered quartz bar processing. Depending on the purpose, cutting is carried out at required angles measured against this crystal axis. The crystal resonator is an electronics part designed to oscillate in a stable manner. At high frequencies, the oscillating element is in inverse proportion to thickness of crystal, meaning the higher frequency is, the thinner crystal is, and vice versa. By applying this characteristic, crystal is cut and smoothed until a targeted frequency (thickness) and size (outer diameter dimension) are available. This process is critical because the property of a crystal resonator is almost decided. The work process requires very fine precise control up to parts per million. In addition, crystal is hard and likely for a brittle fracture to occur, so it is incredible to see it bent with ease. But if the processing continues and crystal becomes very thin, it could be bent as shown in the photo.
(3) Frequency adjustment and cleaning
The crystal blank, after being cut and ground with grinding material, has distortions with small cracks and stains on the surface, which together is called the affected layer. In order to remove such distortion and stain, chemicals are used to smooth out and clean up the surface of the crystal. At this point, the fine-tuning of the frequency is conducted as well. Up until this point, some of the crystal blanks turn out to be smaller than a grain of rice and thinner than paper. This change is really a big surprise.
(4) Making on electrode
By the processes so far, targeted frequency and size have been accomplished. However, it is impossible to have oscillation of an electric signal because the electric connection can not be made. So this comes in where the metal film of gold, silver or other metals are glued onto the crystal blank by the method of base plating. If current is supplied to this metal film, the crystal blank oscillates and frequency is available. This is the application of an inverse piezoelectric effect.
(5) Adhering and sealing of crystal blank
In order to connect the electrode-formed crystal blank to a circuit board, crystal blank is stuck to the ceramics pack
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